The present invention relates to devices employed for monitoring variations in color of objects such as articles of manufacture for which it is desired to maintain consistency of color or, stated in other words, detect excessive variation in the color of the articles.
Color detectors of this sort can be employed on assembly lines to monitor the variation of color of articles of manufacture during the final stage of quality inspection as, for example, monitoring the variation in color of pharmaceutical capsules to prevent inclusion of capsules of the wrong color in a package containing capsules color-coded for a specific pharmaceutical content. In such an application, it is commonplace to have the color detector disposed at a stationary position along a moving conveyor for inspecting articles as they pass the stationary detector. Such an arrangement often results in a variation in the distance of the surface of the targeted article from the detector, which affects the intensity of the diffused reflected light from the targeted article; and, thus affects the level of reflected light detected by the sensor and usually results in an erroneous signal from the detector.
Thus, it has been desired to find a way or means of accommodating variations in the distance of an article to be monitored for color variation from the color sensor or detector in a manner which is simple and inexpensive, and may be employed on a continuous basis for sensing variations in color in articles in a mass-production application. It has further been desired to provide such accommodation for variations in distance for sensing color of a target article without the need for plural detectors each calibrated to sense the color of an object at a different distance.